Harmonic composite grind

ABSTRACT

In order to improve the riding characteristics of automobile tires, known tire grinding machines are employed to reduce the force reaction between the tire and load wheel to predetermined limits both as to the fundamental of the force reaction and a harmonic of the fundamental. Automatic switching from one to the other modes of grinding is provided.

Unite States Patent UPPER LIMIT Monajj em Nov. 26, 1974 [5 HARMONICCOMPOSITE GRIND 3,574,973 4/1971 Rader 51/165 n en Freydoun ajjMayfield, Ky. 3,724,137 4/1973 Hofelt SI/106 R [73] Asslgnee: iggf sgflggfi gfig Primary Examiner-Harold D. Whitehead p Attorney, Agent, orFirmKemon, Palmer & [22] Filed: Feb. 21, 1974 Estabrook [21] Appl. No.:444,491

Related U.S. Application Data 57 ABSTCT [62] Division of Ser. No.241,246, April 5, 1972, Pat. No.

3,317,003. In order to improve the ridlng characteristics of auto- 7mobile tires, known tire grinding machines are em- 52 11.s.c1. 51/165 R,51/106 R p y to reduce the force reaction between the tire 51 1111. c11324!) 99/16 and load wheel to predetermined limits both as to the [58]Fi ld f S h n 51/D1(} 33 106 165 R fundamental of the force reaction anda harmonic of the fundamental. Automatic switching from one to the [56]Referen e Cit d other modes of grinding is provided.

UNITED AT PATENTS 3 Claims, 2 Drawing Figures 3,553,903 7/1967 Christie51/165 R RADIAL CONPOSlTE 0 32 78 UPPQR T6 LIMIT col/PAR, 1 1, 56

34 RELA LOWER OUTPUT LIMIT 74 mm TUGRIND liR lllll v AND moot(ALTERNATE) w 1 F GRIND LOGIC COMPARATORBO +1ov 5x111 ADJUST 11111101110ANGLE 38 LOOl MARK SERV TOlPPERGl'INJ ZERO CONTROL OUTPUT l 1 All?SERVO-VALVE 40V CROSSING L UPPER 11cm SENSOR RETRACT RS RELA LUIIERLIMIT 1 40 0V /m TOLNERGRN) mm P SERVO-VALVE comm Y LOWER 0cm SENSOR 42DELAY HARMONIC COMPOSITE GRIND f This is a Division of Application Ser.No. 241,246

filed Apr. 5, 1972, now US. Pat. No. 3,817,003, dated June 18, 1974.

BACKGROUND OF THE INVENTION Tire grinding machines are known whichautomatically remove small amounts of rubber from the shoulders of thetire in response to automatically sensed vari ations in the forcereaction between the tire and a load wheel. Examples of such machinesmay be found in at least the following US. Pat. Nos:

3,553,903 dated Jan. 12, 1971 3,574,973 dated Apr. 13, 1971 As iswell-known in this art, the grinding of tread shoulders of tires is aneffective method for reduction of radial force variations whichotherwise occur to an objectionable degree when uncorrected tires areused on automotive vehicles. At least at the present state of the art,the technology of manufacturing tires is incapable of producing a timewhich is completely uniform. The variations which can occur in bothmaterial and assembly of material during the manufacturing process arealso well known and need not be detailed here. Suffice to say, vehiclemanufacturers now specify limits of force variations in tires which willbe acceptable to them depending upon the tire size and the particularmanufacturer. Some manufacturers place more emphasis on the limits ofthe fundamental force variation while others are more concerned with aharmonic of the fundamental force variation. In some cases higherharmonic values are allowed and vice-versa.

The problem of ultimately providing the best possible quality of ride iseven more complex than mere variations in tire uniformity alone becausethese variations combine with such other factors as natural resonancesof the wheel and suspension systems of the vehicle itself. In any event,it has been amply demonstrated that on the average, grinding of theshoulder portions of tires both as to the fundamental of force variationand as to a harmonic (usually the first) of the same force variation iseffective to produce very substantial im- SUMMARY OF THE INVENTION Thepresent invention provides a programable system for increasing thecapability of existing tire force grinding machines by incorporatingprogrammed switching from grinding based upon the composite or actualforce variation to grinding based on a harmonic of force variation.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a schematic block diagram ofa preferred embodiment of the present invention applied to a known tiregrinder control arrangement; and

FIG. 2 is an amplified block diagram of the comparator 80 of FIG. 1.

DETAILED DESCRIPTION OF THE DRAWING A load wheel is driven from a sourceof power not shown bringing the wheel in contact with and loading a tire12 mounted in a special chuck so as to be freely rotatable by a powersource not shown. The radial force variations between the tire and theload wheel are sensed by a load cell 14 to produce electrical signalswhich mean analog of the radial force variations. The signal is then fedto asignal conditioner 16, an amplifier l8 and a filter and zerosuppressor 20. The peak to peak value is then detected in a peakdetector 22 and then registered and stored in memory circuits 24 and mayalso be numerically displayed on a meter 26.

An acceptable lower limit of the value of the composite force variationis programmed into the system by the setting of a potentiometer 28.Similarly, another value-representative of the maximum amount beyondwhich a tire may not be ground is programmed into the system through thesetting of a potentiometer 30. The

actual value of the radial composite force signal is then compared withthe signals corresponding to the setting of potentiometers 28 and 30 bymeans of upper and lower limit comparator circuits 32 and 34. Theoutputs of the'comparator circuits are utilized to drive a relay circuit36 which is operative to energize various marking devices which willmark the tire, preferably in a coded designation, indicative of thevalue of its composite force variation.

The composite force variation signal as it appears at the input of thepeak detector 22 is also fed to a pair of servo-amplifiers 38 and 40 theoutputs of which control servo-valves one of which is schematicallyindicated at 41. The servo-valves control movement of the grindingmembers into and out of contact with the shoulders of the tire. Sincethe grinding wheels are displaced circumferentially of the tire from thepoint of engagement of the tire with the load wheel 10, thiscircumferential spacing must be taken into consideration in order thatthe actual grinding will remove rubber at the desired location on thetire. The composite force variation signal therefor, before reaching theservo amplifiers 38 and 40, is fed through an analog delay circuit 42which exactly compensates for the time that it takes that portion of thetire which has created a composite force variation signal sensed by theload cell 14 to travel from the point of contact with the load wheel 10to the location of the grinding wheels.

In accordance with the present invention, the composite force variationsignal as it appears at the input of the peak detector circuit 22 isalso fed to a harmonic loop arrangement including an amplifier 44 and apair of integrators 46 and 48. The output of integrator 46 will be ananalog signal proportional to a harmonic of the radial composite forcevariation signal fed into the amplifier 44. While this could be anyharmonic, for the purposes of this disclosure it will be referred to asthe first harmonic. In any event, the signal is fed to a register andstorage means 49 similar to the storage means 24 used to store thecomposite radial force signal. Just as in the case of the compositeforce signal, an acceptable value of the first harmonic of the compositeforce signal is programmed into the system by setting a potentiometer 50and likewise a signal corresponding to the maximum amount beyond whichthe tire may not be ground is programmed into the: system by the settingof a potentiometer 52. The actual value of the first harmonic signal isthen compared in upper and lower limit comparator circuits 54 and 56 theoutputs of which are utilized to drive a relay circuit 58 which willenergize various marking devices to mark the tire with a code indicativeof the value of the first harmonic of the composite force variation.

The signal corresponding to the composite radial force variation whichappears at the input of the peak detector 22 is also fed to a firstharmonic loop which includes an inverting amplifier 60 and integrators62 and 64. Under the conditions to be hereinafter described, the signalappearing at the output of the integrator 62, which is the firstharmonic component of the composite force variation, is arranged to befed to the servo-amplifiers 38 and 40 in the same manner as thecomposite force variation signal in'order that the tire may be ground inaccordance with the first harmonic signal.

Irrespective of which of the two signals is being used at the time tocontrol the servo-amplifiers 38 and 40, two potentiometers 66 and 68associated with the amplifier 70 which drives the servo-amplifiers 38and 40 through the analog delay 42 are used to program the minimum grindlevel and the maximum grind depth respectively.

The output of the comparator circuits 32, 34, 54 and 56 are allcontinuously monitored by a grind comparator circuit 72. When grindingin accordance with either the composite radial force signal or theharmonic signal has proceeded to a point where the variations are withinthe pre-programmed acceptable limits, a relay 74 is energized to close anormally open circuit which will retract the grinders from the tire.Relays 76 and 78 are also subject to control by the grind comparator 72and are effective when energized to open the circuits to potentiometers50 and 28 respectively and substitute for these potentiometers otherpotentiometers 29 and 51. This permits grinding the tire to values whichare below the original set lower limits established by the setting ofpotentiometers 28 and 50.

In order to control automatically a switch-over from the radialcomposite force signal to the first harmonic of that signal as an inputto the grind servo-amplifiers 38 and 40, the output of the lower limitcomparator 34 is fed to the input of a further comparator circuit 80.This circuit controls a relay 82 which controls contacts 82a, 82b, 82cand 82d in such manner as to reverse their conditions when the relay 82is energized. In its unenergized state therefor the composite forcevariation signal is fed to the servo-amplifiers through the normallyclosed contact 82a. Whenever the relay 82 is energized however contacts82a are opened and contacts 82b are closed thereby establishing an inputto the amplifier 70 the analog delay 42 and the servogrind amplifiers 38and 40 from the output of integrator 62 which is the first harmonic ofthe composite radial force variation signal.

Referring now to FIG. 2 which is a schematic block diagram of thecomponents of the comparator circuit 80, this circuit includes a pair ofsumming network and input buffer amplifiers 84 and 86 which drive a pairof DC amplifiers 88 and 90 respectively. The outputs of the DCamplifiers are in turn fed to a pair of trigger circuits 92 and 94 thecombined outputs of which drives the relay 82 through a transistor 96.

On the input side of the comparator circuit 80, are arranged a pair ofpotentiometers 98 and 100. The setting of these potentiometers providesa programmed analog signal which is compared with the output of thelower limit comparator 34. When the latter signal reaches a valuecorresponding to the setting of the potentiometers, the relay 82 isenergized to connect the output of integrator 62 to the grind servos 38and 40 by opening 820 and closing 82b. Contacts 820 and 82d are used toswitch the soft spot signal of composite force into the grind amplifierwhen the tire is to be ground on composite response or to a negativefixed value when the tire is to be ground on a harmonic response.

From the foregoing it will be apparent to those skilled in this art thatthere is herein disclosed a new and useful system for controlling tiregrinding machines which is effective to grind within predeterminedlimits based on the composite radial force variations and thenautomatically to switch to a first harmonic of the composite radialforce signal and to again grind the tire to within predetermined limitsbased on the harmonic signal. The order of grinding of course can bereversed if desired.

' While a preferred embodiment of the invention has been herein shownand described, applicant claims the benefit of a full range ofequivalents within the scope of the appended claims.

I claim:

1. Apparatus for automatically grinding pneumatic tires to correct bothfor radial composite road force variations and a harmonic of said forcevariations comprising in combination:

means mounting a tire for rotation about a first fixed axis;

grinding means for removing small amounts of rubber from the treadshoulder of a tire;

a load wheel mounted on an axis parallel to said first axis; means torotate said tire in contact with said load wheel so as to positivelyrotate said load wheel;

means for sensing force variations caused by the force reactions betweensaid tire and said load wheel and for converting said force variationsto first analog electrical signals;

peak detector means connected to receive said signals;

storage means connected to receive and store said signals; meansproviding a pair of further signals, the magnitude of which arepredetermined and proportional to the acceptable amount of compositeradial force variation and the maximum amount beyond which a tire maynot be ground;

comparator means connected to receive and compare said first analogsignals with said further pair of signals;

means for driving said grinding means if said analog lies between saidpair of signals and to continue to grind said tire until said analogreaches a predetermined value;

means for generating second analog signals which are a harmonic of saidfirst analog signals;

means for comparing said second analog with predetermined referencesignals; means for driving said grinding means if said second analoglies between predetermined limits; and

means for terminating the grinding of the tire when said second analogsignal falls to a predetermined value.

2. Apparatus as defined by claim 1 including means for automaticallyswitching the control of said grinding means from one to the other ofsaid analog signals.

3. Apparatus as defined by claim 1 in which said second analog signalsare the first harmonic of the first analog signals.

1. Apparatus for automatically grindIng pneumatic tires to correct bothfor radial composite road force variations and a harmonic of said forcevariations comprising in combination: means mounting a tire for rotationabout a first fixed axis; grinding means for removing small amounts ofrubber from the tread shoulder of a tire; a load wheel mounted on anaxis parallel to said first axis; means to rotate said tire in contactwith said load wheel so as to positively rotate said load wheel; meansfor sensing force variations caused by the force reactions between saidtire and said load wheel and for converting said force variations tofirst analog electrical signals; peak detector means connected toreceive said signals; storage means connected to receive and store saidsignals; means providing a pair of further signals, the magnitude ofwhich are pre-determined and proportional to the acceptable amount ofcomposite radial force variation and the maximum amount beyond which atire may not be ground; comparator means connected to receive andcompare said first analog signals with said further pair of signals;means for driving said grinding means if said analog lies between saidpair of signals and to continue to grind said tire until said analogreaches a predetermined value; means for generating second analogsignals which are a harmonic of said first analog signals; means forcomparing said second analog with predetermined reference signals; meansfor driving said grinding means if said second analog lies betweenpredetermined limits; and means for terminating the grinding of the tirewhen said second analog signal falls to a predetermined value. 2.Apparatus as defined by claim 1 including means for automaticallyswitching the control of said grinding means from one to the other ofsaid analog signals.
 3. Apparatus as defined by claim 1 in which saidsecond analog signals are the first harmonic of the first analogsignals.